As a magnetic sensor, a device has conventionally been well known which has Hall elements provided on a semiconductor substrate and a magnetic substance (magnetic flux concentrator) that is mounted on the Hall elements and has a magnetic convergence function, and which causes magnetic convergence and detects the magnetic field intensity thereof with the Hall elements.
FIG. 1 is a structural view for explaining this type of magnetic sensor. A semiconductor circuit 1 comprises a semiconductor substrate 3 and Hall elements 4a and 4b provided in the semiconductor substrate 3. On the semiconductor circuit 1, a protective layer 5 and an adhesive layer 6 are formed successively, and a magnetic flux concentrator 2 is provided thereon.
As to the magnetic sensor consisting of a combination of the Hall elements with the magnetic substance (magnetic flux concentrator) having the magnetic convergence function, there is a Patent Document 1, for example. The device described in Patent Document 1 relates to a magnetic field direction detecting sensor capable of deciding the directions of a magnetic field two dimensionally. It has a magnetic flux concentrator with a flat shape, a first Hall effect device, and a second Hall effect device, and the Hall effect devices are placed at edge regions of the magnetic flux concentrator.
A device described in Patent Document 2 is a magnetic sensor with the same structure as that shown FIG. 1, and relates to a technique for matching the horizontal direction magnetic field sensitivity and the vertical direction magnetic field sensitivity.
A device described in Patent Document 3 has the following structure. It brings a probe card, which includes a coil for applying a magnetic field to a magnetic sensor, into contact with one of the magnetic sensor modules each having a magnetic sensor and a digital signal processing unit. A test of the magnetic sensor is made by checking the digital signal processing unit via the probe card while generating a magnetic field by supplying a current to the coil. Then, correction values of the magnetic sensor corresponding to the test result are stored in a storage of the magnetic sensor module via a probe card.
Furthermore, as for the sensitivity correction of a Hall element, the following structure is known. As shown in FIG. 2, a vertical direction magnetic field generating coil is placed right under a Hall element to generate a vertical magnetic field component, and the Hall element detects the vertical magnetic field component generated by the vertical direction magnetic field generating coil, thereby correcting the self-sensitivity of the Hall element. Concrete contents thereof are described in Non-Patent Document 1.
The foregoing Patent Document 1 discloses the following. It has a construction that includes the Hall elements provided on the semiconductor substrate and the magnetic substance (magnetic flux concentrator) which has a magnetic convergence function and is mounted on the Hall elements, and that carries out magnetic convergence with the magnetic substance and detects the magnetic field intensity with the Hall elements. In the magnetic sensor that detects the magnetic fields in the horizontal direction and vertical direction to detect 2-axis or 3-axis magnetic signals orthogonal to each other, the magnetic sensitivity varies to the horizontal direction magnetic field and to the vertical direction magnetic field. Accordingly, it is necessary to match the sensitivity between the individual axes.
The present applicant proposes in the foregoing Patent Document 2 a technique for matching the magnetic sensitivity in the horizontal direction and vertical direction by arranging a lot of elements for detecting magnetism in the vertical direction. The method, however, cannot correct sensitivity variations involved in the element sensitivity variations of the individual magnetic sensors or the misalignment of the magnetic substance.
The foregoing Patent Document 3 discloses the following. It brings the probe card, which has the coil for applying the magnetic field to the magnetic sensor, into contact with one of the magnetic sensor modules each including the magnetic sensor and digital signal processing unit, and tests the digital signal processing unit via the probe card while generating the magnetic field by supplying the coil with the current, thereby checking the sensitivity of the magnetic sensor and carrying out the sensitivity correction.
In the Patent Document 3, to check whether the circuit block operates in accordance with the function, it is necessary to perform operations such as providing the external probe card with the coil for generating the magnetic field, and taking the trouble to bring the probe card into close contact with the IC wafer for the measurement. At the same time, to calibrate the magnetic field the coil generates, it is necessary to carry out complicated operations such as preparing a wafer calibrated in advance, and correcting the coil after measuring the wafer once. This presents a problem of entailing test cost.
In such circumstances, it has been investigated to solve the foregoing problems by incorporating an internal coil into a magnetic sensor without using the external coil. Mounting the internal coil on the magnetic sensor makes it possible: 1) to check the functional operation during manufacturing and at shipping; 2) to carry out, for each axis, the sensitivity correction for the variations in the process dependence of the output sensitivity and for the sensitivity deviation of the circuit blocks; 3) to obviate the need for providing a magnetic field test coil (external coil) for generating a uniform magnetic field region in an appropriate range on a test board. This makes it possible to test many magnetic sensors collectively, thereby offering an advantage of reducing the test cost.
In addition, Non-Patent Document 1 discloses the following, for example. It places the vertical direction magnetic field generating coil for generating the vertical magnetic field component right under the Hall element on the same silicon substrate, and detects the vertical magnetic field component generated by the vertical direction magnetic field generating coil with the Hall element, thereby measuring the sensitivity and carrying out correction.
This construction, however, cannot generate any magnetic fields other than the vertical direction magnetic field. Accordingly, as for the magnetic sensor construction, which has sensitivity to 2-axis or 3-axis magnetic components orthogonal to each other, the sensitivity of all the axes cannot be measured with the internal coil.
As described above, the devices described in Patent Documents 1 to 3 and Non-Patent Document 1 are the following. They achieve the sensitivity correction of the Hall element or magnetic sensor in various forms. All the documents have contents relating to magnetic sensors capable of detecting 2-axis or 3-axis magnetic fields orthogonal to each other. However, they do not disclose any concrete configuration for measuring the sensitivity in the individual axial directions of the magnetic sensor without using the external coil, that is, any configuration of arranging internal coils for sensitivity measurement between the magnetic substance and Hall elements.
The present invention is implemented to solve the foregoing problems. Therefore it is an object of the present invention to provide a magnetic sensor and sensitivity measuring method thereof having a function of measuring the sensitivity in the individual axial directions of the magnetic sensor without using an external magnetic field source for sensitivity measurement in a 2-axis or 3-axis magnetic sensor including a semiconductor substrate having a plurality of Hall elements provided separately from each other and a magnetic substance placed on the semiconductor substrate.
Patent Document 1: Japanese Patent Laid-Open No. 2002-71381.
Patent Document 2: Japanese Patent Laid-Open No. 2004-257995.
Patent Document 3: Japanese Patent Laid-Open No. 2007-24518.
Non-Patent Document 1: “Autocalibration of silicon Hall devices” (P. L. C. Simon et al. Sensors and Actuators A 52 (1996) 203-207.